OT -automotive air conditioning troubleshooting questions

[Hannibal]

2010 Ford Escape. Just bought cheap for a stepdaughter who can't quit wrecking cars.

So the air conditioning doesn't work, heat does. Compressor was running when A/C was turned on. Threw the gauge set on it and -0- press on both the high and low side. Tried adding a can of refrigerant just to confirm suspicions. Both sides equalized at 80 psi and still no cooling. Seems to be holding that pressure but obviously there's a leak of some sort somewhere.

So now my questions.

Given what I know about air conditioning systems the low pressure switch is bad. I can remove the A/C clutch relay and the compressor stops. Won't restart when the relay is replaced until the vehicle is shut-off and restarted. As the compressor has been running for no telling how many hours with no refrigerant it's gotta be bad evidenced by the fact that the low pressure and high pressure side equalize when refrigerant was added but nothing more.

Since the compressor is ruined it likely contaminated the system with debris which would be difficult to remove at best and likely to cause a new compressor to fail eventually if installed.

And unless the original refrigerant leak happened to be in the failed compressor that leak would still need to be located and repaired.

Is this about right or am I off in the weeds somewhere?

Thanks in advance and any constructive input would be greatly appreciated.

[Tall]

Any time the compressor is replaced the dryer needs to be replaced also. I would start by replacing those two items then try pulling a vacuum. If it holds vacuum for 24 hours then and only then would you install refrigerant.

[sigep1764]

The high and low pressure lines will need to be replaced as well. Metal shards and contaminants hide in them as well as in the dryer. All these parts can be found on rockauto.com and replaced with simple hand tools. When buying the compressor, get the one pre filled with oil. Then fill with the appropriate amount of refrigerant. I like to leave a window down and leave one hand in front of a vent. As soon as it feels cold, stop adding refrigerant. This amount should coincide with the amount in pounds of required refrigerant labeled on the system. If labeled in pounds, remember that cans of refrigerant come in 12 Oz cans. 16oz is one pound. I had to redo the entire system on my 84 Jimmy and this is how I did it.

[Dave W.]

Are you saying that with the compressor running the high and low sides were 80PSI? If so, either the compressor is not pumping or the orifice tube is damaged - has a hole in it, it is not restricting the flow of refrigerant. Your best bet is to take it to a shop for repair, but if you want to try it yourself.....
First try to locate the leak using soapy water, unless you have the leak detection equipment.
Then recover the existing refrigerant.
Remove the orifice tube and inspect - if it has a hole in it, metal is all through the system, all the hoses, compressor, accumulator, orifice tube, evaporator and condenser need replaced.
If the tube is clean, you can probably get by with just a compressor, orifice tube and accumulator. If it has metal on it, add the condenser as well as hoses from the compressor to the evaporator.
Also replace any parts that were leaking. I would replace the low pressure switch.
Pull a vacuum on the system, then recharge it to factory specs with the correct refrigerant.
Good luck.

[Plate plinker]

Agree change everything. If you’re crazy enough to do it yourself (like me) it still would not cost that much.

[Tall]

Typically (check this) the dryer also is a cleaner and has a screen to protect the rest of the system from metal shards. There will be normally a short flex line from the compressor to the dryer. That line can be re - used provided you clean it with a solvent like isopropyl alcohol.

[Recycled bullet]

2010 Ford Escape. Just bought cheap for a stepdaughter who can't quit wrecking cars.

So the air conditioning doesn't work, heat does. Compressor was running when A/C was turned on. Threw the gauge set on it and -0- press on both the high and low side. Tried adding a can of refrigerant just to confirm suspicions. Both sides equalized at 80 psi and still no cooling. Seems to be holding that pressure but obviously there's a leak of some sort somewhere.

So now my questions.

Given what I know about air conditioning systems the low pressure switch is bad. I can remove the A/C clutch relay and the compressor stops. Won't restart when the relay is replaced until the vehicle is shut-off and restarted. As the compressor has been running for no telling how many hours with no refrigerant it's gotta be bad evidenced by the fact that the low pressure and high pressure side equalize when refrigerant was added but nothing more.

Since the compressor is ruined it likely contaminated the system with debris which would be difficult to remove at best and likely to cause a new compressor to fail eventually if installed.

And unless the original refrigerant leak happened to be in the failed compressor that leak would still need to be located and repaired.

Is this about right or am I off in the weeds somewhere?

Thanks in advance and any constructive input would be greatly appreciated.

Hello Hannibal. IF the system is properly charged with the correct charge Mass of r134 and the compressor is in fact running and the pressure is the same on both the high and low side service ports THEN the compressor has failed because it is unable to generate pressure.

The proper functionality of automotive air conditioning hinges on the relationship between charge Mass and internal AC system volume and all the electronic components that are required to keep this safe and functional.

If you are unsure as to the condition or maintenance history of the system then an AC service can be good so you can establish a baseline what direction the diagnostics need to go. AC system diagnostic is critical on knowing the facts.

When you do an AC service recover the refrigerant and then vacuum it out to boil the humidity out of the lines. This can be critical step for a vehicle that has been discharged and without pressure for an extended period of time, all the humidity in the air reacts with the oil inside the AC system and breaks down and causes failures especially if people just keep topping off the freon without sucking out the water humidity.

When you start charging refrigerant start the car put the AC on max and then start filling refrigerant through the low side or suction service port. The compressor will then kick on so continue looking at the pressure gauges as you fill freon.

You are done filling when high side pressure is approximately 150-175 lb and low side pressure is approximately 40-50 lb when the compressor runs with the cooling fans engaged. This way you can be reasonably sure of correct charge mass amount even if you do not have a laboratory scale or a $5,000 AC service machine.

After you've charged the correct amount freon then you can charge or add the dye. I like to use a fluorescent pag oil dye. The parts store sells an AC system oil injector tool -one side of it fits the low side service port the other end of it is a piston with a screw handle. You put the oil in it turn the screw handle and it charges the oil. Charge that in through the low side service port then degrease both ports really well with brake cleaner. Then periodically you can shine an UltraViolet flashlight into the engine bay- any leaks will glow like aliens blood. If you do this at night then you can easily check the the compressor, condensor, all the pipes hoses and seals, and the drain tube underneath the car and see if the evaporator is cracked and leaking freon there.


The system is designed in such a way that if the pressure is too low (undercharge) the compressor will not kick on, and if the pressure is too high (overcharge or blocked condensor) the compressor will not kick on.

If the compressor clutch is turning then the safety switches and the relay and the fuses are all functional.

[Hannibal]

Thanks to all, I really appreciate it.

Now to decide if I want to work on this myself.

[rockrat]

Have your stepdaughter help you work on it. If she has a bit of sweat/blood equity in the car, she might be a bit more careful when driving it(or maybe not). Alternately, if she is just going to wreck it, why fix the A/C?

You have gotten pretty good advice already, I cannot add anything more from what has been given. Good luck with the repairs

[Hannibal]

Have your stepdaughter help you work on it. If she has a bit of sweat/blood equity in the car, she might be a bit more careful when driving it(or maybe not). Alternately, if she is just going to wreck it, why fix the A/C?

You have gotten pretty good advice already, I cannot add anything more from what has been given. Good luck with the repairs

That girl can't fix a sandwich without setting the kitchen on fire. Already had a big argument with my wife over buying another car. But thanks for helping me make up my mind. She wants it fixed she can find the money to pay a shop to do it. It's not going to be quick, easy or cheap. I'm out.

[MaryB]

Looking under the hood of my Escape there is no way in heck I would attempt a repair. There is ZERO spare room... To swap my battery I have to take apart the entire cold air intake up to the throttle body... The AC parts are buried!

[45DUDE]

Most vehicles have a low pressure switch which kicks the compressor off when low. Maybe someone wired around it? The hoses are good for 300+ pounds of pressure. If you have gauges you can remove a valve and hook an air compressor to the high side-100 pounds will work-then soap water to check for leaks. This is a cheap no cost way to do your self IF you can see the fittings. With the correct gauges and fittings you can suck the system to 18 pounds before installing freon<should be 30 but 18 works> using another car for the the vacuum source. You can use the same car but then would be too hot to mess with. I've been in your shoes and it's a money pit that doesn't stop. They are fixing to turn the water or electricity off -Then you have to cough up a deposit because they waited until the last minute-can I borrow <give> $300 --My transmission went out and I can't get to work.

[HATCH]

I don't have a lot to add to this conversation that hasn't already been added.

If you had zero PSI when you hooked the gauges to it AND your sure the gauges work then you got a leak somewhere.
If the compressor was still running with zero PSI and after putting a can in it reads 80 on both high and low then you do need a compressor for sure.

The first course of action is to find the leak before you replace anything.
Components like the evaporator core (under the dash) or condenser (in front of the radiator) are you big worries.
You can do what someone suggested above about just replacing everything but that will cost over $1K to do that and that's you doing the work.

Plan on replacing the compressor, expansion block, filter drier, and if that model has one the orifice tube (which I don't think it does).
From Rock Auto
$230 UAC KT4877 - kit includes compressor, expansion block, and filter drier.

You can use compressed air to blow out the evap and condenser.


I have a company that I use for work that deals specifically with refrigeration.
Everything from Commercial units, heavy equipment and school buses.
When they come across a unit that has NO freon then they fill the system to 150 PSI (using compressed gas) and leak check with with soapy water.
After they located and repaired the leak(s) they vacuum it down.
It is possible that you have a system that will hold a vacuum (-30) but still leaks.
It is possible that you have a system that will hold pressure but still leaks (compressor seals are the worst).
But if you can get it to hold pressure and you get it to -30 on vacuum then chances are your system is good.

I ran into a issue with a system that pressure tested fine with no leaks but would in fact over time leak down with use.
Turns out a hose fitting was bad. It would not leak unless the engine was running and the vibration caused it.


After I typed all of that, I have a suggestion that is cheap and will give you a idea on what your in to.
Go take it to a shop. Pay for a AC diagnostic to be done. Typically its like $50.
That will at least give you a idea on what parts to replace.